Panetta sent a 24-page missive to New York federal judge Alvin Hellerstein, arguing that release of agency cables describing tough interrogation methods used on al-Qaida suspects would tell the enemy far too much about U.S. counterterrorism work.

The CIA director filed the papers in a lawsuit brought by the American Civil Liberties Union. The suit has already led to the unveiling of Bush administration legal memos authorizing harsh methods — among them waterboarding, a type of simulated drowning, and slamming suspects into walls — and a fight over releasing long-secret photos of abused detainees.

"I have determined that the disclosure of intelligence about al-Qaida reasonably could be expected to result in exceptionally grave damage to the national security by informing our enemies of what we knew about them, and when, and in some instances, how we obtained the intelligence," Panetta wrote.

Panetta acknowledges in the court papers that the CIA destroyed 92 videotapes of detainee interrogations that took place in 2002. Officials have previously said that a dozen of those tapes showed the so-called "enhanced interrogation techniques," which critics call torture. The destruction of the videotapes has spurred a criminal investigation into why they were destroyed.

The tapes — and the interrogations — are also an issue in the ACLU's lawsuit.

The CIA is fighting efforts to force release of the documents, including dozens of agency cables. The cables, Panetta said, describe in detail the methods used on terror suspects, the information gleaned from them and what U.S. officials still did not know at the time the suspects were being questioned.

The CIA last month denied a request by former Vice President Dick Cheney to declassify secret memos that detail whether valuable intelligence was gained from the use of the harsh interrogation techniques. Cheney said the documents show that the tactics prevented terrorist attacks and saved lives, contrary to the Obama administration's criticism of the Bush-era policies.

President Barack Obama also said last month he would try to block the court-ordered release of photos showing U.S. troops abusing prisoners, reversing his position out of concern the pictures would "further inflame anti-American opinion" and endanger U.S. forces in Iraq and Afghanistan.